NUEVO LAREDO, Mexico, July 14 (Reuters)
- Thousands of U.S. and Mexican trucks hauling goods across the border
were backed up on Wednesday after severe flooding blocked a key trade route
in northern Mexico, truckers and authorities said.

Some 22,000 trucks were unable to deliver
goods between the Mexican border cities of Nuevo Laredo and Monterrey and
the Texas city of Laredo as days of rain from Hurricane Alex and a second
tropical storm swamped the highway from Monterrey, Mexico's national cargo
truckers' chamber said.

The road that was shut since Friday was
partially reopened on Wednesday but water levels were still impeding many
trucks from moving and priority was being given to vehicles carrying fresh
produce and emergency aid for flooded Mexican towns.

"We have 22,000 trucks that cannot
deliver on both sides of the border and are completely stalled," said
Refugio Munoz, the truckers' chamber president. "We don't see trucks
moving again until Friday," he told Reuters.

It was not clear what the full economic
impact of the blockage would be, but Nuevo Laredo Mayor Ramon Garza said
it was substantial. The route carries some 40 percent of trade over the
U.S.-Mexico border.

"This represents millions and millions
of dollars lost," said Garza.

Munoz said Mexican truckers had been
using an alternative route since Friday, reaching Nuevo Laredo via Reynosa
across from McAllen, Texas, but that the highway suffered damages from
flooding and partly collapsed on Monday.

"This could affect factories because
they rely on auto parts from the United States on a just-in-time basis
and supplies are not getting through," he added.

Octavio Gonzalez, director of a private
sector group that promotes regional trade, said many factories were very
anxious because of the lack of auto part deliveries. "We are getting
calls from desperate companies because of the lack of supplies that have
stopped production lines or because exports are stalled," Gonzalez
said, without giving more details.

Supermarkets in Nuevo Laredo were largely
empty because trucks could not reach the city. "A lot of things are
scarce, most of all fresh produce," resident Alma Rosa Vela said.

A tropical depression dumped heavy rains
on the Mexico-Texas border on July 8 days after Hurricane Alex flooded
the region. Alex battered Monterrey as a Category 2 storm, killing 12 people,
ripping apart highways and causing $700 million of damage. (Additional
reporting by Caroline Stauffer and Tim Gaynor in Mexico City and Gabriela
Lopez in Monterrey; writing by Robin Emmott; editing by Mohammad Zargham)